Experimental design and RSM on the recovery of Ni (II) ions by ELM using TX-100 as a biodegradable surfactant.

The present work deals with the extraction and pre-concentration of nickel (II) ions using emulsified liquid membrane (ELM) in the presence of di- (2-ethylhexyl) phosphoric acid (D2EHPA) as an extractant. The emulsion stability was achieved by the biodegradable surfactants Triton X-100 addition diluted in kerosene. Influence of operating conditions that affect ELM performance were investigated. A comparative study between the optimization parameters of this process was carried out both experimentally and with the Response Surface Methodology (RSM), in accordance with the Box-Behnken matrix. The following parameters were investegated: D2EHPA / Triton X-100 ratio between 0.5 and 3.5, initial concentration of the feed phase between 200 and 500 ppm and pH of the feed phase from 2.5-10. The transport of Ni (II) ions was evaluated according to the extraction yield as an analytical response and the optimal conditions were determined. It was found that the calculated values being in good agreement with experimental data that under the optimized conditions ([Ni] = 350 ppm, Vagitation = 200 rpm,  = 20 min and pH = 6.6), Ni (II) ions extraction was recorded more than 94% of efficiency.